He told the Standard: "The RMT leadership is demonstrating once again its utter contempt for commuters and business alike. No one will be forced out of a job, no one will lose pay. Less than 3 per cent of journeys start at a ticket office, at a cost of £50 million - by saving that money we can help keep fares down.

"This action is supported by just 30 per cent of the RMT membership. It's unacceptable, and hard working Londoners will suffer the most."

Business leaders warned that the strikes would harm the capital, and they backed the controversial modernisation programme that is being opposed by the unions.

Baroness Jo Valentine, chief executive at London First, said: “The news of this latest strike threat baffles those millions of Londoners who rely on the Tube.

“Everyone was led to believe that all of the outstanding issues had been resolved in February - otherwise, why did the unions call off their strike action then? Whatever the pros and cons of the respective sides’ positions, the prospect of more disruption is a depressing one for Londoners.

“Revamping the Tube so that it meets the 21st century needs of the World’s leading city is vital. But surely this shouldn’t yet again be at the expense of Tube users - as ever, the innocent victims, particularly those who don’t get paid if they can’t get to work. Why should they have to endure frustration and huge inconvenience yet again?”

David Cameron: Said the Tube strike is 'unjustified' and 'unacceptable'

The Conservatives estimated the cost to the capital of lost trade from delays and disruption would be at least £150 million - enough to generate enough tax income to pay for 2,000 nurses, 1,750 teachers or 1,400 police officers.

Their figure was based on a London Chambers of Commerce study estimated that the major Tube strike in 2007 cost £48 million a day in lost productivity, worth around £60 million at today’s prices. The Tories estimated a £30 million per day cost because Transport for London predict that half of services will run this time.

Members of the Rail, Maritime and Transport (RMT) union are due to walk out from 9pm on Monday April 28 for two days, and for another three days from 9pm on Monday May 5. It is part of a long-running protest against ticket office closures and modernisations that the union claims will cost jobs, undermine services and jeopardise safety.

TfL is warning customers that services will be affected from around 9.30pm on the evening of Monday. The disruption will be worst on Tuesday and Wednesday when no underground services will run before 7am and a reduced service will operate. Services will end at 11pm but passengers are being warned that the last trains out of central London could depart as early as 9.30pm.

The strike is being timed just before a memorial service to the RMT’s former leader Bob Crow who died suddenly last month.

The RMT’s acting general secretary Mick Cash said: “Instead of attacking tube workers who are fighting to defend jobs and safety, David Cameron should be hauling in his Tory colleague Boris Johnson to explain why he has turned his promise to Londoners not to close ticket offices in its head and is now hell bent on axing every single one of them.

“We will not allow the future of the Tube to be turned into a battleground in the war between Cameron and Johnson for the Tory party leadership.”